Retention for bonded hollow fan blade cover

ABSTRACT

A two part airfoil has a suction side, a pressure side, a rib extending from one of the pressure side or the second side, the rib having a groove therein, and a riblet extending from an other of the pressure side or the suction side, the riblet fitting within the groove.

BACKGROUND

This invention relates to improvements in hollow metal propellers andfan blades adapted primarily for use in aviation service.

It is well known that propeller and fan blades may be hollow and havestiffening ribs disposed therein. The ribs are typically welded to oneplate or the other, or to a propeller shaft.

SUMMARY

According to an embodiment disclosed herein, a two part airfoil has asuction side, a pressure side, a rib extending from one of the pressureside or the second side, the rib having a groove therein, and a ribletextending from an other of the pressure side or the suction side, theriblet fitting within the groove.

According to a further embodiment disclosed herein, a two-part airfoilincludes a suction side, a pressure side, a rib extending from one ofthe pressure side or the second side and having a groove therein. Thegroove has a first contour and a riblet extending from an other of thepressure side or the suction side has a second contour fitting withinthe first contour of the groove such that an effect of tear and shearforce affecting said suction side and said pressure side are lessened .

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of the disclosed examples willbecome apparent to those skilled in the art from the following detaileddescription. The drawings that accompany the detailed description can bebriefly described as follows.

FIG. 1 shows a prior art reinforcing rib of an airfoil attached to acover of an airfoil.

FIG. 2 shows an embodiment of a reinforcing rib of an airfoil attachedto a cover of an airfoil.

FIG. 3 shows an airfoil incorporating the ribs of FIG. 2.

FIG. 4 shows a top view of the air foil of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a prior art view of a two-part airfoil 10 is shown.The airfoil 10 has a suction side cover 15 and a pressure side 20. Thesuction side cover 15 is attached to a rib 25 depending from an inside23 of the pressure side 20. The rib is attached to the suction sidecover 15 by a bond 30 such as glue, welding or the like.

Referring now to FIGS. 2 and 3, an airfoil 110 is shown. The airfoil 110has a suction side cover 115 and a pressure side 120. The pressure side120 has an inner surface 127 from which ribs 125 extend towards thesuction side cover 115. The ribs 125 have a longitudinal groove 128formed therein. The suction side cover 115 has plurality of riblets 130extending from an inner surface 131 thereof towards the pressure side120. The groove may be machined or cast or forged into the ribs 125.Though the groove 128 is shown with a rectangular contour and theriblets 130 also have a rectangular contour, other mating riblet 130contours and groove 128 contours are contemplated herein providing suchother contours provide increased gluing area and less motion between ariblet 130 and the groove 128.

A glue 133, such as an epoxy or a urethane, may be used to join the ribs125 and the riblets 130 together within the groove 128. One can seethat, by joining the ribs 125 and the riblets 130 together within thegroove 128, the amount of glue 133 used to join the suction side cover115 and the pressure side 120 is increased by the amount of glue 133placed on the sides 135 of the riblet, as compared to the prior art. Theadded glue 133 provides a concomitantly stronger bond between thesuction side cover 115 and the suction side 120. If a urethane glue isused, the urethane glue may provide damping between the suction sidecover 115 and the pressure side 120

Moreover, by placing the riblet 130 within the groove 128, the effect ofoperative forces, which may cause shear and tearing motion between thesuction side cover 115 and the pressure side 120, are minimized becauseof a mechanical bond between the ribs 125 and the riblets 130 as thesuction side cover 115 and pressure side 120 react to operation withinan airstream. This mechanical advantage minimizes the effect of tear andshear force affecting suction side cover 115 and pressure side 120 ofthe airfoil 110.

Referring now to FIGS. 3 and 4, an interior view of the suction sidecover 115 and the pressure side 120 are shown. The inner surface 127 ofthe pressure side has an trench 140 (see FIG. 4) that approximates thesides 145 and the bottom 147 of the elbow-shape of the suction sidecover 115. The trench is spaced from the leading edge 154 and thetrailing edge 150 and the base 160 of the airfoil 110. The pressure side115 has a first plurality 165 of ribs 125 extending from the trench 140near the base 160 to the trench 140 adjacent the leading edge 154 of thetrench and a second plurality 175 of ribs 125 extending from the trench140 near the trailing edge 150 to the trench 140 near the leading edge154.

The suction side cover 115 has a set of corresponding riblets 130 thatfit within the grooves of the first plurality 165 of ribs 125 and thesecond plurality 170 of ribs 125. The second plurality of ribs 170extend from near the trailing 150 to near the leading edge 154 ortowards the blade tip 173. The suction side cover 115 has a bead 180extending along its outside edge 185 that mates with the trench 140.

To construct the airfoil, glue 133 is placed in the grooves 128 in theribs 125 and the trench 140 and the riblets 130 are pressed into thegrooves 128 and the bead 180 is pressed into the trench 140.

Although a combination of features is shown in the illustrated examples,not all of them need to be combined to realize the benefits of variousembodiments of this disclosure. In other words, a system designedaccording to an embodiment of this disclosure will not necessarilyinclude all of the features shown in any one of the Figures or all ofthe portions schematically shown in the Figures. Moreover, selectedfeatures of one example embodiment may be combined with selectedfeatures of other example embodiments. For instance, the riblets 130 maybe attached to the pressure side 115 and the ribs 125 may be attached tothe cover 120.

The preceding description is exemplary rather than limiting in nature.Variations and modifications to the disclosed examples may becomeapparent to those skilled in the art that do not necessarily depart fromthe essence of this disclosure. The scope of legal protection given tothis disclosure can only be determined by studying the following claims.

1. A two part airfoil comprising: a suction side, a pressure side, a rib extending from one of said pressure side or said second side, said rib having a groove therein, and a riblet extending from an other of said pressure side or said suction side, said riblet fitting within said groove.
 2. The two part airfoil of claim 1 further comprising: a glue disposed between said rib and said riblets wherein motion between said suction side and said pressure side is damped.
 3. The two part airfoil of claim 2 wherein said glue is a urethane glue.
 4. The two part airfoil of claim 1 wherein said groove is longitudinal.
 5. The two part airfoil of claim 1 wherein one of said suction side and said pressure side has a trench adjacent an outer profile thereof and wherein an other of said suction side and said pressure side has a bead that fits in said trench.
 6. The two part airfoil of claim 5 wherein said trench is adjacent a leading edge and a trailing edge of said airfoil.
 7. The two part airfoil of claim 5 wherein said trench is adjacent a leading edge and a base of said airfoil.
 8. The two part airfoil of claim 7 wherein a rib extends from said trench adjacent a base of said airfoil to said trench adjacent a leading edge of said airfoil.
 9. The two part airfoil of claim 8 wherein said trench is adjacent a leading edge and a trailing edge of said airfoil.
 10. The two part airfoil of claim 9 wherein a rib extends from said trench adjacent said leading edge to said trench adjacent said trailing edge.
 11. The two part airfoil of claim 5 wherein said trench is in said pressure side.
 12. The two part airfoil of claim 1 wherein said rib extends from said pressure side.
 13. The two part airfoil of claim 1 wherein said riblet extends from said suction side.
 14. A two-part airfoil comprising: a suction side, a pressure side, a rib extending from one of said pressure side or said second side, said rib having a groove therein said groove having a first contour, and a riblet extending from an other of said pressure side or said suction side, said riblet having a second contour fitting within said first contour of said groove such that an effect of tear and shear force affecting said suction side and said pressure side are lessened.
 15. The two-part airfoil of claim 14 wherein said first contour and said second contour mate.
 16. The two-part airfoil of claim 14 wherein said first contour and said second contour are rectangular.
 17. The two part airfoil of claim 14 further comprising: a glue disposed between said first contour and said second contour wherein motion between said suction side and said pressure side is damped.
 18. The two part airfoil of claim 17 wherein said glue is a urethane glue. 